CN103030493A - Method for preparing ethylene and acetylene from ethane - Google Patents

Abstract

The invention discloses a method for preparing ethylene and acetylene from ethane, which belongs to the technical field of chemical industry. Ethane or a mixture of low-carbon alkanes rich in ethane and oxygen are preheated to 200-700°C respectively, enter the mixer for rapid mixing, ignite through the burner, enter the combustion chamber for reaction, and obtain 700-1500°C high temperature product. At the outlet of the combustion chamber, the high-temperature product is quenched by the quenching agent, and the further reaction consumption of ethylene and acetylene is terminated in time. Compared with the traditional high-temperature steam cracking of ethane to produce ethylene, the invention directly utilizes the heat generated by the partial oxidation of ethane to generate high temperature to crack ethane to produce ethylene and acetylene. Depending on the operating conditions, the selectivity of ethylene is 30-70%, the selectivity of acetylene is 10-30%, and the total selectivity of ethylene and acetylene is 50-85%.

Description

A kind of method utilizing ethane to prepare ethylene and acetylene

technical field

The invention relates to a method for preparing ethylene and acetylene from ethane, which belongs to the technical field of chemical material preparation.

Background technique

Ethylene and acetylene are important basic organic chemical raw materials, and their downstream processed products mainly include polyethylene, ethylene oxide, ethylene glycol, polyacrylonitrile, polyvinyl chloride, polyvinyl alcohol, etc. The industrial production of ethylene mainly includes high-temperature steam cracking of ethane and naphtha high-temperature cracking. The former is difficult to generate high-temperature steam, consumes a lot of energy and has low thermal efficiency, and the latter relies heavily on petroleum resources. Acetylene was first produced by the calcium carbide method. The advantages of this method are high product purity and easy operation. The disadvantages are high power consumption and serious environmental pollution. The production of acetylene by partial oxidation of natural gas does not produce solid waste and is also a by-product of synthesis. gas.

The non-catalytic partial oxidation of ethane has the advantages of simple technical route and long-term stable operation because it does not use a catalyst. The advantages of the partial oxidation method are: the raw materials are easy to obtain, the price is cheap, and the heat generated by the partial oxidation of ethane is directly used to crack the ethane that has not undergone oxidation reaction to prepare ethylene and acetylene, which can greatly improve the heat utilization rate, and the by-product tail gas can be used to produce synthetic ammonia. or methanol. This process involves high temperature, rapid mixing, strong turbulence, millisecond-level reaction and rapid termination reaction, etc., which put forward very high requirements for optimal operation and safety control. Among them, the rapid mixing of ethane and oxygen and the rapid cooling of high-temperature products are the key to realize this process. key.

In the Middle East and other by-product ethane regions, high-temperature steam cracking of ethane is widely used to produce ethylene. Although it has a greater cost advantage than high-temperature cracking of naphtha, it is difficult to generate high-temperature steam in this process, and the volume ratio of water vapor to ethane The maximum is close to 3, and the cracking of ethane through the heat transfer of the coil is an indirect heat exchange, the heat utilization efficiency is low, and there are high requirements for the material of the reactor. ,

However, there are certain problems in the partial oxidation of ethane to ethylene and acetylene. For example, the temperature has a great influence on the reaction activity. Due to the limitation of the ignition delay time of ethane, the preheating temperature cannot be too high; when the preheating temperature is low, the reaction The increased amount of oxygen required will result in an increase in the proportion of ethane participating in the partial oxidation reaction, thereby reducing the selectivity of ethane to ethylene and acetylene. As the reaction time increases, the proportion of methane will also increase.

Currently there is a patented technology for the partial oxidation of ethane to ethylene. Most patents focus on the field of catalytic partial oxidation. In US 3541179, the reaction temperature is 600-1000°C, and the reaction to generate ethylene proceeds very quickly, and the indirect heat exchange efficiency of water vapor is difficult to guarantee; in the US 3080435 reaction process, there is chlorine element, and it is difficult to purify the generated olefins, and chlorine Corrosion to the reactor is very serious; US 4524236 and US 4568790 The reaction temperature is greatly reduced, only 200 ° C, the ethylene selectivity is as high as 70~90%, but the single-pass conversion rate of ethane is lower than 30%. Non-catalytic partial oxidation technology is also patented. CN 1269341A has a reaction temperature of 700-900°C, an inert gas content of 10-80%, and an ethylene selectivity of over 70%. This patented method still requires external heating to provide high temperature to maintain stable reaction Carried out, the energy consumption is higher.

Contents of the invention

The object of the present invention is to provide a method for preparing ethylene and acetylene from ethane, which has the advantages of simple technical route and long-term stable operation.

Technical scheme of the present invention is as follows:

The invention provides a method for preparing ethylene and acetylene by utilizing ethane or a mixture of low-carbon alkanes rich in ethane, which is used for producing ethylene and acetylene, and is realized through the following technical scheme.

The flow rate of ethane or ethane-rich low-carbon alkane mixture and oxygen is accurately controlled by a meter, and the volume ratio of the two is 10-1. The pressure of ethane or ethane-rich low-carbon alkane mixture and oxygen entering the mixer 1~5atm. The heating of ethane or a mixture of low-carbon alkanes rich in ethane and oxygen can be directly heated to 200~700°C through a fireplace, enter the mixer for rapid mixing, and ignite the small flame of the permanent lamp formed by auxiliary oxygen at the outlet of the mixer and enter the combustion chamber react.

Ethane or a mixture of low-carbon alkanes rich in ethane and oxygen are heated and then enter the mixer for rapid mixing. After preheating, the ignition delay time of the mixture is shortened, and the mixture of ethane or a mixture of low-carbon alkanes rich in ethane and oxygen passes through the mixer The dwell time is 10~500ms. In order to fully mix ethane or ethane-rich low-carbon alkane mixture with oxygen, the length of the mixer is 0.5-10m. In order to ensure that there will be no abnormal flow phenomena such as back mixing and backflow during the mixing process, the mixer needs to be designed as a structure with a gradually expanding diameter, and the gradual expansion angle α of the mixer along the gas flow direction is 0~15°. The gas velocity of the gas mixture passing through the burner hole is 30~150m/s.

The high-temperature product at the outlet of the combustion chamber needs to be quenched to 80~200°C within a few milliseconds, and the quenching agent water sprayed at a high speed needs to maintain an oblique angle with the horizontal plane. This structure can shorten the quenching of the high-temperature product and completely terminate the product. The distance along the axial direction required for deep cracking, the quenching agent injection direction is obliquely upward and the angle between the horizontal plane is 0~45°. The quenched product enters the separation system, where ethylene, acetylene and synthesis gas are separated.

The source of ethane is ethane-rich natural gas containing saturated alkanes such as methane, ethane, propane, butane, refinery gas, and coalbed methane. After desulfurization and denitration treatment, no further purification is required. The oxygen purity is industrial purity.

The material used to process the mixer is stainless steel, and the material used to process the burner and combustion chamber is a high temperature resistant material, such as quartz, ceramics, stainless steel, etc.

In order to solve the problem of high difficulty in steam cracking of ethane to produce ethylene by indirect exchange of steam and low heat efficiency of indirect heat exchange, the present invention proposes to use partial oxidation method to prepare ethylene from ethane or a mixture of low-carbon alkanes rich in ethane And acetylene, using the heat generated by partially oxidized ethane to generate high temperature to crack ethane to produce ethylene and acetylene.

Compared with the prior art, the present invention has the following outstanding advantages and effects.

① Ethane or ethane-rich mixture of low-carbon alkanes and oxygen are preheated to 200-700°C, the activity of ethane increases, and the selectivity of ethane to ethylene and acetylene is as high as 50-85%.

② By adjusting the ratio of ethane or ethane-rich low-carbon alkane mixture to oxygen, the generation of ethylene and acetylene can be controlled, increasing the controllability of industrial production.

③ In addition to ethylene and acetylene, the reaction products also have a large amount of synthesis gas, which can be used in the synthesis of ammonia or methanol to improve industrial competitiveness.

④ Since no catalyst is used in this process, there is no problem of catalyst deactivation, and it has the characteristics of long-term operation.

Description of drawings

Fig. 1 is a schematic diagram of the structure and principle of a method for preparing ethylene and acetylene from ethane provided by the present invention.

Fig. 2a is a schematic longitudinal section of a swirl mixer, and Fig. 2b is a schematic cross section of a swirl mixer.

Fig. 3a is a schematic longitudinal section of a distributor-type mixer, and Fig. 3b is a schematic diagram of a cross-section of a distributor-type mixer.

Figure 4 is a schematic diagram of the burner structure.

Fig. 5a is a front view of the annular quencher (using a perforated structure), and Fig. 5b is a cross-sectional view of Fig. 5a.

In the figure: 1-Oxygen inlet; 1a-Oxygen inlet of swirl mixer; 1b-Oxygen inlet of distributor mixer; 1c-Oxygen nozzle of distributor mixer; 2-Ethane inlet; 2a-Swirl mixer The first ethane inlet of the device, 2b-the second ethane inlet of the swirl type mixer, 2c-the third ethane inlet of the swirl type mixer, 2d-the fourth ethane inlet of the swirl type mixer; 2e-distributor Type mixer first ethane inlet, 2f-distributor type mixer second ethane inlet, 2g-distributor type mixer ethane nozzle; 3-mixer; 3a-swirl type mixer; 3b-distributor Type mixer; 4-burner; 5-auxiliary tube; 6-combustion chamber; 7-quencher; 8-gas product exporter; 9-annular quencher; Side opening.

Detailed ways

The working principle, reactor structure and process for preparing ethylene and acetylene from ethane or ethane-rich low-carbon alkane mixture of the present invention will be described in detail below in conjunction with the accompanying drawings.

Fig. 1 is a schematic diagram of the structure and principle of a method for preparing ethylene and acetylene from ethane provided by the present invention. Normal temperature ethane or low-carbon alkane mixture rich in ethane and normal temperature oxygen are accurately controlled by the meter, exchange heat with the heat exchanger or be heated to 200~700°C by the heating furnace, and pass through the oxygen inlet 1 and the ethane inlet 2 Enter the mixer 3 for fast and thorough mixing; the mixed ethane or ethane-rich low-carbon alkane mixture and oxygen are ignited in the combustion chamber 6 by the small flame formed by the auxiliary oxygen tube 5 at the burner 4, and enter the combustion chamber 6 to react. A high temperature product with a temperature of 700~1500°C is generated. According to one embodiment of the present invention, the annular quencher 7 at the outlet of the combustion chamber sprays quenchant at high speed to quench the high-temperature product to 80-200°C, and the deep cracking reaction of ethylene and acetylene is terminated. According to another embodiment of the present invention, the 700-1500°C high-temperature product is first quenched to 500-600°C, and then the heat is recovered through indirect heat exchange. The gas mixture is connected to the ethylene and acetylene cryogenic separation device through the gas product exporting device 8 to obtain the product ethylene, acetylene and synthesis gas.

Shown in Fig. 2 is that the oxygen after heating passes through the swirl type mixer oxygen inlet 1a that the top of swirl type mixer 3a inserts and sprays from the middle, mixes with from the first ethane inlet 2a of swirl type mixer, swirl type The second ethane inlet 2b of the device, the third ethane inlet 2c of the swirl type mixer, and the fourth ethane inlet 2d of the swirl type mixer are injected into the ethane or the mixture of low-carbon alkanes rich in ethane for mixing. Oxygen is sprayed out through the uniformly distributed small holes in the middle tube, and ethane or a mixture of low-carbon alkanes rich in ethane is sprayed into the mixer wall from four branches to form a swirl flow. In the mixer with a gradually expanding diameter Mix completely and thoroughly. Fig. 3 is that the heated oxygen passes through the gas and the heated ethane or ethane-rich low-carbon alkane mixture distributor type mixer 3b structure to realize mixing, and the heated oxygen passes through the distributor type mixer oxygen inlet 1b and the homogenizer The distributor-type mixer oxygen nozzle 1c is connected, and the heated ethane or ethane-rich low-carbon alkane mixture passes through the first ethane inlet 2e of the distributor-type mixer, and the second ethane inlet 2f of the distributor-type mixer It is connected with the ethane nozzle 2g of the uniform distributor type mixer, and the oxygen nozzle and the ethane or ethane-rich low-carbon alkane mixture nozzle are arranged at intervals. This arrangement shortens the oxygen and ethane or ethane-rich low The diffusion distance required for the complete mixing of the carbon alkane mixture can be achieved in a short time to achieve rapid and complete mixing.

The intake pressure of ethane or a mixture of low-carbon alkanes rich in ethane and oxygen is 1-5 atm, preferably 1-3 atm, more preferably 1-2 atm.

The flow rate of ethane or a mixture of low-carbon alkanes rich in ethane and oxygen is accurately controlled by a meter, and the volume ratio of ethane or a mixture of low-carbon alkanes rich in ethane and oxygen is 10 to 1.0, preferably 5 to 1.5, more preferably 3~2.

The heating of ethane or a mixture of low-carbon alkanes rich in ethane and oxygen can be directly heated by a fireplace, or it can be heated by high-temperature waste heat after the high-temperature product is quenched; the heating of ethane or a mixture of low-carbon alkanes rich in ethane and oxygen The preheating temperature is 200-700°C, preferably 450-700°C, more preferably 600-700°C for oxygen, and more preferably 450-550°C for ethane or a mixture of low-carbon alkanes rich in ethane.

Ethane or ethane-rich low-carbon alkane mixture and oxygen are heated and then enter the mixer for rapid mixing. The ignition delay time of the preheated mixture is shortened, and ethane or ethane-rich low-carbon alkane mixture needs to be realized in a short time It is completely mixed with oxygen, and its residence time is 10~500ms, preferably 30~300ms, more preferably 80~150ms.

The gas velocity of ethane or a mixture of low-carbon alkanes rich in ethane and oxygen passing through the burner is 30-150m/s, preferably 50-120m/s, more preferably 80-100m/s.

In order to achieve rapid and complete mixing of ethane or ethane-rich mixture of low-carbon alkanes and oxygen, the length of the mixer is 0.5-10m, preferably 1-8m, more preferably 2-5m.

In order to ensure that there are no abnormal flow phenomena such as back-mixing and reflux during the mixing process, the mixer needs to be designed as a structure with a gradually expanding diameter. The gradual expansion angle α of the mixer along the gas flow direction is 0~15°, preferably 3~12°. More preferably 5~10°.

The high-temperature product at the outlet of the combustion chamber needs to be quenched to 80~200°C within a few milliseconds, and the quenching agent sprayed at a high speed needs to maintain an oblique angle with the horizontal plane. This structure can shorten the quenching of the high-temperature product and completely terminate the product depth For the distance along the axial direction required for cracking, the angle between the jet outlet of the quencher and the horizontal plane is 0-45°, preferably 10-30°, more preferably 15-20°.

According to one embodiment of the present invention, the mixture quenched to 80-200°C enters the product separation device to obtain the products ethylene, acetylene and synthetic synthesis gas.

According to one embodiment of the present invention, the mixture quenched to 500-600°C enters the heat exchanger for indirect heat exchange to recover heat, and then enters the product separation device to obtain the products ethylene, acetylene and synthetic synthesis gas.

Definition of product carbon-based selectivity and ethane conversion:

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \%</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="6"\; label="h"\; filenames="HDA00002573844000011.png,HDA00002573844000043.png"\; state="\{\{state\}\}">h</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}$

${\mathrm{<span\; class="notranslate">\; x</span>}}_{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \%</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="6"\; label="h"\; filenames="HDA00002573844000011.png,HDA00002573844000043.png"\; state="\{\{state\}\}">h</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}$

是乙烷转化率，

是乙烷摩尔浓度。S _i is the selectivity of a certain carbon-containing substance, C _i is the molar concentration of the carbon-containing substance, n _i is the number of carbon atoms in the carbon-containing substance, ∑C _i ×n _i is the ratio of all detected carbon-containing substances The sum of the product of concentration and its number of carbon atoms,

is the ethane conversion rate,

is the molar concentration of ethane.

The method for producing ethylene and acetylene through the partial oxidation of ethane will be described in detail below in conjunction with preferred specific examples.

Example 1:

The preheating temperature directly affects the reactivity of ethane and oxygen. The higher the preheating temperature, the shorter the residence time required for the reaction between ethane and oxygen, and the higher the selectivity of the target products ethylene and acetylene. Therefore, the preheating temperature was investigated. Effect of heat temperature on the process. The pressure of the reaction system is 1 atm, the volume ratio of ethane to oxygen is 3.3:1, the residence time of the reaction gas is 10 ms, and the preheating temperature is 200-600 ° C. The reaction results are listed in Table 1.

Table 1 Effect of different preheating temperatures on the oxidative cracking of ethane to ethylene and acetylene

Example 2:

The volume ratio of ethane or a mixture of low-carbon alkanes rich in ethane and oxygen has a great influence on the reaction activity, especially the intensity of the reaction process. The lower the volume ratio, the more intense the reaction process and the shorter the residence time required for the reaction , which is beneficial to increase the total yield of the target product ethylene and acetylene; but if the volume ratio is too low, the reaction temperature will be too high, and more ethylene will generate acetylene within the same residence time, and even deep cracking into carbon black, while the volume ratio will decrease , will also greatly increase the selectivity of carbon oxides, so the influence of the volume ratio of ethane to oxygen on the process was investigated. The pressure of the reaction system is 1 atm, the preheating temperature of ethane and oxygen is 500°C, the residence time of reaction gas is 10ms, and the volume of ethane and oxygen is 10~2. The reaction results are listed in Table 2.

Table 2 Effect of different volume ratios of ethane and oxygen on the oxidative cracking of ethane to ethylene and acetylene

Example 3:

With the increase of residence time, the conversion rate of ethane will increase, but the target products ethylene and acetylene will be deeply cracked and methanated at high temperature, and the overall selectivity will decrease. Therefore, the influence of residence time on this process was investigated. The pressure of the reaction system is 1 atm, the volume ratio of ethane to oxygen is 3.3, the preheating temperature is 500°C, and the residence time is 5-20ms. The reaction results are listed in Table 3.

Table 3 Effects of different residence times on the oxidative cracking of ethane to ethylene and acetylene

Example 4:

Methane, propane, and butane in the ethane-rich mixture of low-carbon alkanes have different effects on the generation of ethylene and acetylene from ethane. At the same preheating temperature, propane and butane are more active than methane, and are more conducive to the generation of ethylene from ethane. The reaction occurs under certain reaction conditions, so the influence of the same proportion of methane, propane and butane in ethane on the formation of ethylene was investigated. The pressure of the reaction system is 1 atm, the ratio of methane or propane or butane to ethane is 1:9, the preheating temperature of the mixture of ethane and methane or propane or butane and oxygen is 500°C, and the residence time of reaction gas is 10ms. Alkanes and methane or propane or butane mixture and oxygen volume are 3.3, and the reaction results are listed in Table 4.

Table 4 Effects of methane, propane and butane on the oxidative cracking of ethane to ethylene and acetylene

Claims (8)

1. method of utilizing ethane to prepare ethene and acetylene is characterized in that the method carries out as follows:

1) ethane or the low-carbon alkanes mixture and the oxygen that are rich in ethane are heated to respectively 200 ~ 700 ° of C, enter mixing tank in 10 ~ 500ms short mix, light via burner and enter the combustion chamber and react, produce 700 ~ 1500 ° of C high-temperature products;

2) utilize anxious water as refrigerant to spray at a high speed at combustor exit, form trim, high-temperature product is chilled to 80 ~ 200 ° of C;

3) product after the chilling enters centrifugal station, obtains ethene, acetylene and synthetic gas.

2. a kind of method of utilizing ethane to prepare ethene and acetylene according to claim 1 is characterized in that: ethane or be rich in the low-carbon alkanes mixture of ethane and the volume ratio of oxygen is 10～1.

3. a kind of method of utilizing ethane to prepare ethene and acetylene according to claim 1 and 2 is characterized in that: ethane or the low-carbon alkanes mixture that is rich in ethane are 30～150m/s with the gas speed by burner after oxygen fully mixes.

4. a kind of method of utilizing ethane to prepare ethene and acetylene according to claim 3 is characterized in that: ethane or be rich in the low-carbon alkanes mixture of ethane and pressure that oxygen enters mixing tank is 1 ~ 5atm.

5. a kind of method of utilizing ethane to prepare ethene and acetylene according to claim 1, it is characterized in that: ethane or be rich in the low-carbon alkanes mixture of ethane and the hybrid mode of oxygen sprays into for the ethane after the heating or the low-carbon alkanes mixture that is rich in ethane oblique lower eddy flow around the mixing tank, the oxygen after the heating sprays from the centre by the pipe of mixing tank top insert.

6. a kind of method of utilizing ethane to prepare ethene and acetylene according to claim 1, it is characterized in that: the hybrid mode of ethane or the low-carbon alkanes mixture that is rich in ethane and oxygen for the ethane after the heating and the oxygen after be connected is connected with spaced gas distributor nozzle by pipeline, spray abundant mixing downwards.

7. a kind of method of utilizing ethane to prepare ethene and acetylene according to claim 1, it is characterized in that: described mixing tank length of mixing 0.5 ~ 10m, mixing tank is 0 ~ 15 ° along the flaring angle α of gas flow direction.

8. a kind of method of utilizing ethane to prepare ethene and acetylene according to claim 6 is characterized in that: described chilling agent emission direction is for being 0 ~ 45 ° with horizontal plane angle obliquely.

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